Broadband switch/coupler

• US 6,388,539 B1
• Filed: 04/16/2001
• Issued: 05/14/2002
• Est. Priority Date: 04/16/2001
• Status: Expired due to Fees

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Rice, Christopher W
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): TAKAOKA, DEAN O
• Application Number:
  US09/835,612
• Time in Patent Office: 393 Days
• Field of Search: 333/25, 333/26, 333/32, 333/258, 330/301, 330/124.D, 330/116, 330/117, 455/3.3
• US Class Current: 333/25
• CPC Class Codes: H03F 3/602 Combinations of several amplifiers

Abstract

Parallel combined redundancy and switched redundancy are provided for active RF devices (i.e., amplifiers) in a cable plant system with a switch/coupler circuit of passive magnetic devices and switches that respond to an amplifier failure by switching the circuit into a combined or switched redundancy mode as needed to maintain a suitable dynamic range of operation. In either redundancy mode, the switch/coupler circuit operates with a constant 3dB reduction of dynamic range.

Claims

1. A method of providing backup for amplifier failure in a coaxial cable plant including a stage of paralleled first and second amplifiers, by the steps of:

arranging for responding to a failure of one of the first and second amplifiers, by;

balancing outputs of the first and second amplifier;

converting the balanced output to an unbalanced state; and

transforming the unbalanced state into an impedance transformer/transmission line state.

2. The method of claim 1 wherein the steps of:

balancing, converting and transforming are achieved through an agency of magnetic flux coupling.

3. The method of claim 1, wherein the step of:

balancing is achieved by bucking of magnetic flux generated by outputs of the first and second amplifier.

4. The method of claim 3, wherein the step of:

converting is achieved by accumulation of magnetic flux generated by outputs of the first and second amplifiers as modulated by the balancing step.

5. The method of claim 4, wherein the step of:

transforming is achieved by using magnetically coupled devices to provide a matching transmission impedance.

6. A broadband switch for coupling and decoupling RF amplifiers from a cable system, comprising;

first and second inputs for receiving first and second RF amplifiers;

a balancing network connected to the first and second inputs by first and second switch devices so as receive an output of a least one of the RF amplifiers and operative for balancing outputs of the first and second RF amplifiers;

a balance-to-unbalance network connected for converting an output of the first and second RF amplifiers to an unbalanced output; and

an impedance matching network for creating a matching impedance for connecting an output of the first and second RF amplifiers to a cable transmission medium.

7. A broadband switch for coupling and decoupling RF amplifiers from a cable system, as claimed in claim 6, comprising;

the balancing network including a magnetic device including magnetically coupled first and second windings connected to and oriented to balanced outputs of the first and second RF amplifiers; and

switches to disconnect a failed amplifier from the balancing network.

8. A broadband switch for coupling and decoupling RF amplifiers from a cable system, as claimed in claim 6, comprising;

the balance to unbalance network including a magnetic device including magnetically coupled first and second windings connected to and oriented to unbalance balanced outputs of the first and second RF amplifiers.

9. A broadband switch for coupling and decoupling RF amplifiers from a cable system, as claimed in claim 6, comprising;

the impedance matching network including a magnetic device having a first pair of coupled windings and a second pair of magnetically coupled windings;

a switch for controllably coupling mid taps of one winding each of said first pair of coupled windings and second pair of magnetically coupled windings; and

an RF output connected to one each of said first pair of coupled windings and second pair of magnetically coupled windings.

10. A method of providing redundancy in provisioning of amplifiers in a cable system;

comprising the steps of

constraining a balance of first and second RF amplifier outputs with a first pair of magnetically coupled windings,

unbalancing the balanced outputs of said first and second RF amplifier outputs with a second pair of magnetically coupled windings to produce an unbalanced amplified signal;

selectively impedance matching the unbalanced output by adjusting an impedance level based on the number of operative RF amplifiers; and

disconnecting a failed amplifier from the step of constraining balance.

11. The method of claim 10, wherein selective impedance matching includes the steps of:

adjusting relative winding ratios in a magnetic device including first and second pairs of coupled windings.

12. The method of claim 10, wherein constraining a balance of first and second RF amplifier outputs with the first pair of magnetically coupled windings and unbalanced with the second pair of magnetically coupled windings includes the steps of:

having the winding orientation of the pair of windings generate opposing flux; and

using the winding EMF to balance the RF amplifier outputs.

13. The method of claim 12, wherein unbalancing the balanced outputs includes a step of:

applying the balanced output to the second pair of magnetically coupled windings which generate additive magnetic flux; and

grounding one of the second pair windings and taking an output from the grounded windings.